1. Field of the Invention
The present invention relates to a 3-terminal capacitor. More specifically, the present invention relates to a 3-terminal capacitor capable of being used as an electromagnetic interference filter, in which an electrostatic capacitance as well as an inductance is formed between its terminals.
2. Description of the prior art
FIG. 11 is a front view showing a conventional 3-terminal capacitor. On a disc-like ceramic unit 1, electrodes 2 are formed on both sides thereof. As shown in FIG. 11, a U-shaped bent lead-wire 3 is fixed on one electrode 2. A straight lead-wire 4 straight is fixed on the other electrode 2. Then, portions of the ceramic unit 1 and electrodes 2 are molded as shown by the dotted line. Thus, inductances L1 and L2 are formed between terminals 3a and 3b by the lead-wire 3 itself, as shown in FIG. 12. In addition, an electrostatic capacitance C in which the ceramic unit 1 serves as a dielectric member is formed between a connection point of the inductance L1 and L2 and a terminal 4a.
In the 3-terminal capacitor as shown in FIG. 11, the electrostatic capacitance is small such as C=0.01 .mu.F, for example. In addition, even when the capacitance is formed by a laminated capacitor wherein a plurality of ceramic units are laminated, the electrostatic capacitance becomes no more than C=0.1 .mu.F, for example.
In addition, the capacitor as shown in FIG. 11, shows a good attenuation characteristic in a high-frequency region more than 50 MHz, but in the case of less than 50 MHz, the attenuation characteristic becomes extremely bad because the inductive reactance of the inductances L1 and L2 becomes small.